Apparatus and method for coating substrates with washcoats

ABSTRACT

The disclosure relates to a substrate coating apparatus that comprises a source of a washcoat; a washcoat showerhead for discharging the washcoat towards an upper surface of a substrate; a conduit fluidly connecting the source of the washcoat to the washcoat showerhead for supplying washcoat to the washcoat showerhead; a headset for engaging the substrate to locate the upper surface of the substrate below the washcoat showerhead; and a vacuum generator for drawing the washcoat discharged from the washcoat showerhead through the substrate. The headset comprises a partition comprising a plurality of holes, the partition being located in between the washcoat showerhead and the upper surface of the substrate when the substrate is engaged in the headset so as to maintain a first gap between a lower face of the partition and the upper surface of the substrate.

The present disclosure relates to apparatus and methods for coatingsubstrates with washcoats. In particular, it relates to the coating ofsubstrates used for purification of exhaust gases.

BACKGROUND TO THE DISCLOSURE

A substrate for purification of exhaust gases may typically comprise amonolithic substrate that is provided with passages for the through-flowof exhaust gases. The substrate may be provided with a coating, whichmay be a catalytic coating. The coating may be applied to the substrateas a washcoat that is passed through the passages of the substrate.Various methods for applying the coating to a substrate are known. Onesuch method involves applying washcoat to a first face of the substrate(e.g. an upper face) and subjecting an opposite, second face (e.g. alower face) of the substrate to at least a partial vacuum to achievemovement of the washcoat through the passages. After coating thesubstrate may be dried and calcined.

The substrate may be configured as a flow-through substrate wherein eachpassage is open at both the first and second faces of the substrate andthe passage extends through the whole length of the substrate.Consequently, exhaust gases entering through a first face of thesubstrate into a passage pass through the substrate within the samepassage until the exhaust gases exit a second face of the substrate.Alternatively, the substrate may be configured as a filter substrate, inwhich some passages are plugged at a first face of the substrate andother passages are plugged at a second face of the substrate. In such aconfiguration, exhaust gases entering through a first face of thesubstrate into a first passage flow along that first passage part-wayalong the substrate and then pass through a filtering wall of thesubstrate into a second passage. The exhaust gases then pass along saidsecond passage and out of the second face of the substrate. Such anarrangement has become known in the art as a wall-flow filter.

The coated flow-through substrate may comprise a three way catalyst(TWC), a selective catalytic reduction (SCR) catalyst, a dieseloxidation catalyst (DOC), a lean NOx trap catalyst (LNT), an ammoniaslip catalyst (ASC), a combined selective catalytic reduction catalystand ammonia slip catalyst (SCR/ASC), or a passive NOx adsorber (PNA).

The coated filter substrate may, for example, be a catalysed soot filter(CSF) comprising an oxidation catalyst, a selective catalytic reductionfilter (SCRF) comprising a selective catalytic reduction (SCR) catalyst,a lean NOx trap filter (LNTF) comprising a NOx adsorber composition, agasoline particulate filter (GPF) comprising a three-way catalystcomposition, or a filter substrate comprising a selective catalyticreduction (SCR) catalyst and an ammonia slip catalyst (ASC).

The substrate may be made or composed of a ceramic material or ametallic material. For example, the substrate may be made or composed ofaluminium titanate, cordierite (SiO2-Al2O3-MgO), silicon carbide (SiC),Fe—Cr—Al alloy, Ni—Cr—Al alloy, or a stainless steel alloy.

The substrate will commonly have a substrate body which has a uniformcross-sectional shape along its longitudinal length. Typically, thesubstrate body may have a circular or near circular shape incross-section, although other cross-sectional shapes are possible, forexample square and rectangular. An upper surface of the substrate bodymay be defined as the face that is positioned uppermost during coatingand likewise a lower surface of the substrate body may be defined as theface that is positioned lowermost during coating. Commonly, the upperface and lower face are planar and orthogonal to the longitudinal axisof the substrate body.

Some specialised substrates may be provided with a non-planar uppersurface and or lower surface. For example, the upper surface may beprovided with a groove or cut-out for receiving another component. Forexample a sensor of an emissions control system may be positioned in usein the groove or cut-out when the substrate is incorporated in anemissions control system. In another example, the upper surface may beconcavely or convexly domed over a part or a whole of the face.

When coating substrates it may typically be desirable to achieve asubstantially ‘flat’ washcoat profile—i.e. achieving a leading ‘front’or ‘edge’ of the washcoat (marking the boundary interface between thecoated and uncoated portions of the substrate) that is substantiallyflat or perpendicular to the longitudinal axis of the passages.

It has been found that applying washcoats to substrates having anon-planar upper surface or lower surface presents specific problems.Washcoat applied to the upper surface may preferentially collect or poolwithin a groove or cut-out. This can lead to difficulties in controllingprecisely the distribution of the washcoat when drawn by vacuum into thesubstrate body, and in particular in achieving a substantially flatwashcoat profile. For example, an uneven, i.e. non-flat, washcoatprofile may be obtained in the substrate when the washcoat issubsequently pulled through the substrate. This may be caused, forexample, by a greater volume of the washcoat overlying the groove orcut-out and so being drawn into the substrate body further in a regionunderlying the groove or cut-out. An uneven washcoat profile can resultin a detrimental effect to the operational efficiency of the substrate.For example, uneven profiles may lead to portions of the substrate beinguncoated (which reduces the catalytic efficiency of the substrate) orportions of the substrate being unintentionally coated more thanonce—where multiple doses of washcoat are applied (which candeleteriously increase the back pressure of the substrate). In somecircumstances washcoat may be fully pulled through the substrate bodyand emerge from the lower surface. This can lead to waste of washcoatand also potentially blocking of the passage openings on the lower faceof the substrate.

Alternatively or additionally, there may be a problem in adequatelysealing the substrate body to prevent loss of washcoat down the sides ofthe substrate body. This can be a particular problem where the groove orcut-out extends to the sidewall of the substrate body. Soiling of thesidewall of the substrate with washcoat can also lead to visualdegradation of the substrate and may obscure visual identificationmarkings which may be provided on the sidewall of the substrate, e.g.tracing barcodes, etc.

Alternatively or additionally, there may be a problem in achieving evenspreading of the washcoat over the upper surface of some substrates eventhough they have a planar upper surface. For example, it may be that fora given substrate there will be a threshold of viscosity below which thewashcoat is absorbed too quickly into the passages and doesn't spreadfully or equally across the upper surface. This may lead to increasedamounts of washcoat entering the passages directly below the washcoatdelivery outlet and hence lead to an uneven washcoat profile.

SUMMARY OF THE DISCLOSURE

In a first aspect the present disclosure provides a method of coating asubstrate with a washcoat, wherein the method comprises the steps of:

-   -   engaging the substrate with a headset of a substrate coating        apparatus so as to locate an upper surface of the substrate        below a washcoat showerhead of the substrate coating apparatus;    -   arranging a partition between the washcoat showerhead and the        upper surface of the substrate, the partition comprising a        plurality of holes and being located in the headset to maintain        a first gap between a lower face of the partition and the upper        surface of the substrate;    -   discharging a washcoat out of the washcoat showerhead onto an        upper face of the partition; and    -   passing the washcoat through the holes in the partition, onto        the upper surface of the substrate and into the substrate, at        least in part by applying a suction force to a lower surface of        the substrate.

In a second aspect, the present disclosure provides a substrate coatingapparatus comprising:

-   -   a source of a washcoat;    -   a washcoat showerhead for discharging the washcoat towards an        upper surface of a substrate;    -   a conduit fluidly connecting the source of the washcoat to the        washcoat showerhead for supplying washcoat to the washcoat        showerhead;    -   a headset for engaging the substrate to locate the upper surface        of the substrate below the washcoat showerhead; and    -   a vacuum generator for drawing the washcoat discharged from the        washcoat showerhead through the substrate;    -   wherein the headset comprises a partition comprising a plurality        of holes, the partition being located in between the washcoat        showerhead and the upper surface of the substrate when the        substrate is engaged in the headset so as to maintain a first        gap between a lower face of the partition and the upper surface        of the substrate.

In a third aspect, the present disclosure provides a substrate coatingsystem comprising the substrate coating apparatus of the above aspectand a substrate, wherein the upper surface of the substrate isnon-planar; and optionally wherein the upper surface of the substratecomprises a shaping, for example a groove or cut-out, which extends tothe sidewall of the substrate thereby defining a gap in the sidewall.

In a fourth aspect, the present disclosure provides a partitionconfigured for use in a substrate coating apparatus, the partitioncomprising a disc-shaped body;

-   -   the disc-shaped body having a thickness between its upper face        and its lower face of between 5 and 15 mm, optionally between        7.5 and 12.5 mm, optionally 10 mm;    -   the partition comprising greater than 500 holes, optionally        greater than 1000 holes, optionally greater than 1500 holes,        optionally greater than 2000 holes;    -   the holes each being between 1 to 3 mm in diameter, optionally 2        mm in diameter;    -   wherein the percentage open area of the partition, defined as        the percentage of the total area of the upper face of the        partition that is comprised by the holes, is between 35 and 55%,        optionally between 40 and 50%, optionally about 45%.

Advantageously, in any of the above aspects the use of the partitionwith its plurality of holes helps to prevent washcoat accumulating in,for example, a groove or cut-out of the upper surface of the substratewhen the upper surface is non-planar. This has been found to result in areduction in deleterious effects on the washcoat profile and a reductionof pull-through of washcoat out of the lower surface of the substrate.

In particular, in any of the above aspects advantageously the suctionforce may be applied within a certain time limit of the washcoat beingdischarged onto the upper face of the partition. For example, this timelimit may be 5 seconds, preferably 3 seconds, more preferably 1 second.This may advantageously limit or prevent the washcoat reaching the uppersurface of the substrate before the suction force is applied. In thisway pooling or accumulation of the washcoat in any groove or cut-out inthe upper surface may be prevented or at least substantially reducedsince washcoat contacting the upper surface of the substrate may beimmediately drawn into the substrate body by the applied suction force.

In addition, in any of the above aspects maintaining the first gapbetween the lower face of the partition and the upper surface of thesubstrate advantageously helps to minimise and or prevent bridging ofthe washcoat between the partition and the substrate before or after thesuction force is applied to the lower surface of the substrate, by forexample, preventing any capillary action between the partition and theupper surface of the substrate.

Any one of the first to fourth aspects may also comprise one or more ofthe following features:

-   -   The partition may be arranged in a fixed relationship in the        headset.    -   The first gap may be between 2 and 7 mm, optionally 5 mm. Thus,        the first gap may be optimised not only to minimise or prevent        bridging of the washcoat but also to control and or limit        further spreading of the washcoat. For example, the        configuration of the washcoat showerhead may be chosen to        achieve a desirable initial distribution of the washcoat onto        the upper face of the partition. It may therefore be desirable        not to have the first gap to be too large otherwise the washcoat        may be subjected to further unwanted disturbance, e.g. from        mixing of separate streams, splashing, bounce-back, etc.        Therefore, a first gap of between 2 and 7 mm has been found most        effective.    -   The partition may be disc-shaped and have a thickness between        its upper face and its lower face of between 5 and 15 mm,        optionally between 7.5 and 12.5 mm, optionally 10 mm. It has        been found advantageous to limit the thickness of the partition        to between 5 and 15 mm so as to minimise the additional        backpressure of the substrate coating system.    -   The partition may be located in the headset to maintain a second        gap between a lower face of the washcoat showerhead and the        upper face of the partition of between 80 and 130 mm. A distance        of between 80 and 130 mm has been found to optimise the        distribution of the washcoat on the upper face of the partition        when deposited by the washcoat showerhead.    -   The partition may comprise greater than 500 holes, optionally        greater than 1000 holes, optionally greater than 1500 holes,        optionally greater than 2000 holes. The holes may each be        between 1 to 3 mm in diameter, optionally 2 mm in diameter. The        percentage open area of the partition, defined as the percentage        of the total area of the upper face of the partition that is        comprised by the holes, may be between 35 and 55%, optionally        between 40 and 50%, optionally about 45%. Advantageously, the        partition may thus be optimised to minimise or prevent seepage        of the washcoat through the partition onto the upper surface of        the substrate until the suction force is applied, while at the        same time limiting the additional back pressure of the system        and providing good distribution of the washcoat across the        partition and hence across the upper surface of the substrate.    -   The headset may further comprise a headset seal and the        partition may be arranged in the headset above the headset seal.    -   As noted, the upper surface of the substrate may be non-planar.    -   Additionally, the upper surface of the substrate may comprise a        shaping, for example a groove or cut-out, which extends to the        sidewall of the substrate thereby defining a gap in the        sidewall.    -   The substrate may be selected from a flow-through substrate        (e.g. a monolithic flow-through substrate) or a filter substrate        (e.g. a wall-flow filter substrate).    -   The washcoat may comprise a catalytic coating. The catalytic        coating may be selected from a three way catalyst (TWC), a        selective catalytic reduction (SCR) catalyst, a diesel oxidation        catalyst (DOC), a lean NOx trap catalyst (LNT), an ammonia slip        catalyst (ASC), a combined selective catalytic reduction        catalyst and ammonia slip catalyst (SCR/ASC), and a passive NOx        adsorber (PNA).    -   The washcoat may have a viscosity of 3 to 9000 cP.

In a fifth aspect, the present disclosure provides a method of coating asubstrate with a washcoat, wherein the method comprises the steps of:

-   -   engaging the substrate with a headset of a substrate coating        apparatus so as to locate an upper surface of the substrate        below a washcoat showerhead of the substrate coating apparatus;    -   discharging a washcoat out of the washcoat showerhead towards        the upper surface of the substrate;    -   drawing the washcoat through the substrate by applying a suction        force to a lower surface of the substrate;        wherein the step of engaging the substrate with the headset        comprises engaging a headset seal of the headset with the        substrate, the headset seal comprising a perimetral portion        extending around the headset and a cantilevered portion        extending down from the perimetral portion which engages against        a sidewall of the substrate.

In a sixth aspect, the present disclosure provides a substrate coatingapparatus comprising:

-   -   a source of a washcoat;    -   a washcoat showerhead for discharging the washcoat towards an        upper surface of a substrate;    -   a conduit fluidly connecting the source of the washcoat to the        washcoat showerhead for supplying washcoat to the washcoat        showerhead;    -   a headset for engaging the substrate to locate the upper surface        of the substrate below the washcoat showerhead; and    -   a vacuum generator for drawing the washcoat discharged from the        washcoat showerhead through the substrate;    -   wherein the headset comprises a headset seal for engaging        against the substrate, the headset seal comprising a perimetral        portion that extends around the headset and a cantilevered        portion that extends down from the perimetral portion and which        is configured to engage against a sidewall of the substrate.

In a seventh aspect, the present disclosure provides a headset seal forengaging against a substrate, the headset seal comprising a perimetralportion for extending around a headset and a cantilevered portion thatextends from the perimetral portion and which is configured for engagingagainst a sidewall of a substrate.

Any one of the fifth to seventh aspects may also comprise one or more ofthe following features:

-   -   The perimetral portion may comprise an annular portion,        optionally a circular or oval portion, that extends fully around        the headset.    -   The cantilevered portion may be arc-shaped.    -   The cantilevered portion may have an arc length of between 105        and 300% of an arc length of the gap in the sidewall, optionally        between 105 and 200% of an arc length of the gap in the        sidewall.    -   The cantilevered portion may subtend a central angle of between        45 and 120°, optionally between 45 and 90°, optionally between        65 and 75°.    -   The cantilevered portion may extend at an angle of between 0 and        15° with respect to a plane perpendicular to the perimetral        portion; optionally at an angle of between 0 and 10° with        respect to a plane perpendicular to the perimetral portion;        optionally at an angle of about 3° with respect to a plane        perpendicular to the perimetral portion.    -   On engaging the substrate with the headset, the cantilevered        portion of the headset seal may flex in a substantially radial        direction.    -   A lower edge of the cantilevered portion may freely project and        may thus be enabled to flex in a substantially radial direction.    -   The cantilevered portion may engage a region of the sidewall of        the substrate having a height of at least 5 mm greater than a        depth of a gap in the sidewall of the substrate.    -   The cantilevered portion may extend down at least 20 mm below a        lower face of the perimetral portion, optionally at least 30 mm        below a lower face of the perimetral portion, optionally at        least 40 mm below a face rim of the perimetral portion.    -   The perimetral portion and the cantilevered portion may be        formed unitarily or may be separate. The perimetral portion and        the cantilevered portion may be formed of different materials.    -   At least the cantilevered portion may be formed from a flexible        material.    -   The cantilevered portion may have a shore hardness of between 35        A and 45 A, optionally of 40 A.    -   The headset may comprise a rigid headset frame supporting the        perimetral portion of the headset seal and the cantilevered        portion of the headset seal may extend below a lower face of the        rigid headset frame.    -   A lower edge of the cantilevered portion may freely project from        the rigid headset frame.    -   The upper surface of the substrate may be non-planar.

The upper surface of the substrate may comprise a shaping, for example agroove or cut-out, which extends to the sidewall of the substratethereby defining a gap in the sidewall, wherein the cantilevered portionbridges over the gap to hinder leakage of the washcoat out of the gapand down the sidewall of the substrate.

-   -   The substrate may be selected from a flow-through substrate        (e.g. a monolithic flow-through substrate) or a filter substrate        (e.g. a wall-flow filter substrate).    -   The washcoat may comprise a catalytic coating. The catalytic        coating may be selected from a three way catalyst (TWC), a        selective catalytic reduction (SCR) catalyst, a diesel oxidation        catalyst (DOC), a lean NOx trap catalyst (LNT), an ammonia slip        catalyst (ASC), a combined selective catalytic reduction        catalyst and ammonia slip catalyst (SCR/ASC), and a passive NOx        adsorber (PNA).

The features of the first to fourth aspects may be combined withfeatures of the fifth to seventh aspects and vice versa. For example, asubstrate coating apparatus may be provided with a partition accordingto the second aspect and a headset seal according to the sixth aspect.

In the present specification all references to viscosity refer to theviscosity of the fluid as measured using a Brookfield RotationalViscometer fitted with a Small Sample Adaptor and link hanging spindlewith the sample temperature controlled at 25° C. Such viscometers areavailable from Brookfield Engineering Laboratories, Inc., Middleboro,MA, USA.

All measurements were taken at a shear rate of 14 s⁻¹. As will be commongeneral knowledge to the skilled person, the spindle, rotational speedand viscometer model were chosen in dependence on the viscosity of thefluid in order to ensure the % viscometer torque has a minimummeasurement greater than 10% and a maximum measurement less than 100%,where this is not possible the % viscometer torque may have a minimummeasurement greater than 0% and a maximum measurement of less than 100%.For the viscosity measurements in the present specification thefollowing spindles were used:

-   -   Viscosity range 3 to 100 cP was measured using spindle SC4-18 at        10.6 rpm on an LV viscometer.    -   Viscosity range 100 to 500 cP was measured using spindle SC4-28        at 50 rpm on an LV viscometer.    -   Viscosity range 500 to 9000 cP was measured using spindle SC4-28        at 50 rpm on an RV viscometer.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

Aspects and embodiments of the present disclosure will now be described,by way of example only, with reference to the accompanying drawings, inwhich:

FIG. 1 is a schematic cross-sectional view of a substrate coatingapparatus;

FIG. 2 is a schematic enlarged view of a portion of FIG. 1 ;

FIG. 3 is a perspective view of a substrate;

FIG. 4 is a schematic view showing a substrate of the type shown in FIG.3 in a portion of a substrate coating apparatus;

FIG. 5 is a perspective view from underneath of a headset seal for asubstrate coating apparatus;

FIG. 6 is a plan view from underneath of the headset seal of FIG. 5 ;

FIG. 7 is a side elevation view of the headset seal of FIG. 5 ;

FIG. 8 is a cross-sectional view of the headset seal of FIG. 5 ;

FIG. 9 is a photograph of a portion of a substrate coating apparatusincorporating a headset seal of the type shown in FIG. 5 ;

FIG. 10 is a cross-sectional view of a portion of a substrate coatingapparatus that incorporates a partition;

FIG. 11 is a perspective view from above of the partition of FIG. 10 ;

FIG. 12 is a plan view from above of the partition of FIG. 10 ;

FIG. 13 is a side elevation view of the partition of FIG. 10 ;

FIG. 14 is a side view of a substrate after coating with a washcoat;

FIG. 15 is a top plan view of a portion of a substrate after coatingwith a washcoat;

FIG. 16 is a side view of a sectioned substrate after coating with awashcoat; and

FIG. 17 is a bottom view of the substrate of FIG. 16 prior tosectioning.

DETAILED DESCRIPTION

As used in this specification and the appended claims, the singularforms “a”, “an” and “the” include plural referents unless the contextclearly indicates otherwise. Thus, for example, reference to a“catalyst” includes a mixture of two or more catalysts, and the like.

As used in this specification the term “about” also includes thespecific value. For example, “about 45%” includes about 45% and also 45%within its meaning.

The skilled reader will recognise that one or more features of oneaspect or embodiment of the present disclosure may be combined with oneor more features of any other aspect or embodiment of the presentdisclosure unless the immediate context teaches otherwise.

FIG. 1 shows a schematic cross-sectional view of a non-limiting exampleof a substrate coating apparatus 1 that may be used for coating asubstrate 10 with a washcoat.

The substrate coating apparatus 1 may comprise a depositor 2 having ahousing 40 containing apparatus for activating a dispensing mechanism.As shown, the dispensing mechanism may comprise a piston 41 which isaxially moveable within a bore 42 to displace a fluid out of an outlet43 towards a conduit 35 located downstream of the depositor 2.

The substrate coating apparatus 1 may further comprises a hopper 3defining a hopper reservoir 30 having an outlet 31 connecting with theoutlet 43 of the depositor 2 via a diaphragm valve 32. The hopper 3 maybe filled with a washcoat that has been formulated and pre-mixed atanother location. The washcoat may be pumped into the hopper reservoir30 or may be fed under gravity into the hopper reservoir 30 throughsuitable conduits.

The outlet 43 of the depositor 2 fluidly connects with the conduit 35which in turn may extend into fluid communication with a dosing valve 4.A washcoat showerhead 5 may be connected to a lower face of the dosingvalve 4 with the washcoat showerhead 5 being positioned above thesubstrate 10.

The substrate 10 may be located and positioned between a headset 6 and apallet insert 8. A vacuum apparatus including a vacuum cone 7 may belocated beneath the substrate 10.

FIG. 2 shows an enlarged portion of the substrate coating apparatus 1 ofFIG. 1 and shows in more detail how the substrate 10 may be positionedrelative to the washcoat showerhead 5 and headset 6.

FIGS. 1 and 2 show the substrate 10 to be of a of the type that has asubstrate body 11 which has a uniform cross-sectional shape along itslongitudinal length. Typically, the substrate body 11 may have acircular or near circular shape in cross-section. The substrate body 11may be positioned to extend between the headset 6 and the pallet insert8 such that an upper surface 12 of the substrate body 11 is uppermostand a lower surface 13 of the substrate body 11 is lowermost. The uppersurface 12 and lower surface 13 are planar and orthogonal to thelongitudinal axis of the substrate body 11.

The headset 6 may comprise a headset seal 15 that engages an upper edgecircumscribing the upper surface 12 of the substrate body 11. Theheadset seal 15 may comprise an annular ring that extends fully aroundthe headset 6.

The washcoat showerhead 5 may be located above the headset 6 and may bepreferably aligned with the headset 6 and substrate 10 such that acentral longitudinal axis, x, of the washcoat showerhead 5 is coincidentwith the central longitudinal axis of both the headset 6 and substratebody 11 as shown in FIG. 2 .

The washcoat showerhead 5 may comprise a showerhead housing 21 to whichmay be coupled, on a lower side, a showerhead plate 23 by means of bolts26. An adaptor plate 27 may be coupled to an upper side of theshowerhead housing 21, also by means of bolts 28.

The showerhead housing 21 may comprise a centrally located aperturedefining an inlet 22 to a showerhead cavity 24 that is defined betweenthe showerhead housing 21 and the showerhead plate 23. The axis of theinlet 22 may be coincident with longitudinal axis x. The adaptor plate27 may also comprise a centrally located aperture, which may becoincident with longitudinal axis x, and sized to receive a centralportion 20 of the showerhead housing 21. The dosing valve 4 may bebrought into, and held in, fluid communication with the inlet 22 of theshowerhead housing 21.

The showerhead plate 23 may be provided with an array of nozzleapertures 25.

In use, diaphragm valve 32 is opened and washcoat is drawn into the bore42 from the hopper reservoir 30 by movement of the piston to the right(as viewed in FIG. 1 ). The diaphragm valve 32 is then shut and the doseof washcoat is then displaced through conduit 35 by action of the piston41 of the depositor 2 moving to the left (as viewed in FIG. 1 ). Thewashcoat passes through the dosing valve 4 and inlet 22 into theshowerhead cavity 24. The washcoat then passes through the nozzleapertures 25 and drops down into contact with the upper surface 12 ofthe substrate 10. The washcoat is then drawn down through the passagesof the substrate 10. Drawing of the washcoat through the substrate 10 isdriven, at least in part, by a suction force applied to the lowersurface 13 of the substrate 10 by the vacuum cone 7.

FIG. 3 shows a substrate 110 which has a substrate body 111 with anupper surface 112, a lower surface 113 and a sidewall 108. An upper edge107 extends around the upper surface 112. The illustrated substrate 110is generally cylindrical in shape with a single, cylindrical sidewall108. However, the substrate 110 may take other forms, such as having anoval, square or rectangular upper surface with one or more, e.g. four,sidewalls.

The upper surface 112 is provided with a groove or cut-out 114,hereinafter called for simplicity “groove 114”. The groove 114 may takemany shapes or forms and be of various lengths. The groove 114 may beshaped and sized to fully or partly receive another component, forexample a sensor of an emissions control system.

The groove 114 results in the upper surface 112 being non-planar. Thegroove 114 may extend across the full diameter of the upper surface 112.Alternatively, as shown in FIG. 3 , the groove 114 may extend acrosspart of the diameter of the upper surface 112. The groove 114 may extendat one or both of its ends to the sidewall 108 so as to define one ormore gaps 109 in the sidewall 108 and one or more breaks in the upperedge 107. As shown in FIG. 3 , a single gap 109 is provided.

The groove 114 may have various cross-sectional shaped when sectionedperpendicular to its length. The groove 114 of FIG. 3 has asemi-circular cross-sectional shape. However, other shapes may be useddependent on the shape of the component to be accommodated by the groove114. The gap 109 may have substantially the same shape as the shape ofthe groove 114.

FIG. 4 illustrates certain aspects of the present disclosure wherein aportion of the substrate coating apparatus 100 according to the presentdisclosure which is modified compared to the substrate coating apparatus1 to allow it to advantageously coat substrates that have non-planarupper surfaces and or lower surfaces. The substrate coating apparatus100 will be described, by way of example only, for coating the substrate110 of FIG. 3 . However, it will be appreciated that this is notlimiting and the substrate coating apparatus 100 may be usedbeneficially for the coating of other substrates.

Features of the substrate coating apparatus 100 that are the same orsubstantially the same as the substrate coating apparatus 1 of FIGS. 1and 2 have been referenced with similar reference numerals, e.g. 1 and101, 10 and 110, and will not be described in further detail. Referenceshould be made to the above description.

However, the headset seal 115 of the substrate coating apparatus 101 isdifferent to the headset seal 15 of the substrate coating apparatus 1shown in FIG. 2 .

In particular, as shown in FIGS. 5 to 8 , the headset seal 115 comprisesa perimetral portion 116 for extending around the headset 106 and acantilevered portion 117 that extends from the perimetral portion 116and which is configured for engaging against the sidewall 108 of thesubstrate 110.

As shown in FIGS. 6 and 7 , the perimetral portion preferably comprisesan annular portion, which may be circular or oval in shape, that extendsfully around the headset 106 when mounted therein. The perimetralportion 116 may define a central aperture 120 surrounded by an inneredge 121. The inner edge 121 may be perpendicular to the faces of theperimetral portion 116. Alternatively, the inner edge 121 may beprovided with a shoulder, chamfer or taper as desired.

The cantilevered portion 117 may be located at or in proximity to theinner edge 121 of the perimetral portion 116. The cantilevered portion117 may be arc-shaped. This may be particularly beneficial where thesidewall 108 of the substrate 110 is cylindrical. The cantileveredportion 117 may subtend a central angle of between 45 and 120°,optionally between 45 and 90°, optionally between 65 and 75°. Thecantilevered portion 117 may alternatively or additionally have an arclength of between 105 and 300% of an arc length of the gap 109 in thesidewall 108, optionally between 105 and 200% of an arc length of thegap 109 in the sidewall 108.

The cantilevered portion 117 may extend down at least 20 mm below alower face of the perimetral portion 116, optionally at least 30 mmbelow a lower face of the perimetral portion 116, optionally at least 40mm below a face rim of the perimetral portion 116.

As viewed in FIGS. 6 and 8 , the cantilevered portion 117 may have adepth, in a radial direction, of between 2.5 to 5.0 mm.

As shown most clearly in FIG. 8 , the cantilevered portion 117 mayextend at an angle α of between 0 and 15° with respect to a planeperpendicular to the perimetral portion 116; optionally at an angle α ofbetween 0 and 10° with respect to a plane perpendicular to theperimetral portion 116; optionally at an angle α of about 3° withrespect to a plane perpendicular to the perimetral portion 116.

The perimetral portion 116 and the cantilevered portion 117 arepreferably formed unitarily, although they may be formed separately andthen mounted together within the headset 106.

The perimetral portion 116 and the cantilevered portion 117 may beformed of different materials, for example differently co-mouldedmaterials. However, it may be preferred that they are formed from asingle material.

At least the cantilevered portion 117 may be formed from a flexiblematerial. The perimetral portion 116 and or the cantilevered portion 117may be formed from material having a shore hardness of between 35 A and45 A, optionally of 40 A. The perimetral portion 116 and or thecantilevered portion 117 may be formed from a rubber, an elastomer, orother sealing material. Non-limiting examples of suitable materials aresilicone rubber and EPDM, for example silicone rubber 40 shore hard andEPDM 40 shore hard.

As shown in FIG. 4 , the headset seal 115 is mounted in the headset 106.The perimetral portion 116 may extend fully around the perimeter of theheadset 106. The cantilevered portion 117 is shown extending down fromthe perimetral portion 116. A lower edge 123 of the cantilevered portion117 may freely project from the frame of the headset and thus be enabledto flex in a substantially radial direction as shown most clearly in thephotograph of FIG. 9 (FIG. 9 also illustrates features of a partition200 which will be described further below).

On engaging the substrate 110 with the headset 106—wherein the substrate110 may be lifted into engagement with the headset 106—the cantileveredportion 117 of the headset seal 115 may flex in a substantially radialdirection to accommodate passage of the substrate 110. The flexibilityof the cantilevered portion 117 and limited arc length of thecantilevered portion 117 may both aid easier and more reliableengagement of the substrate 110 with the headset 106 during lifting ofthe substrate. Thus, some tolerance for lateral misalignment of thesubstrate 110 with the headset 106 can be tolerated and adjusted for byflexing of the cantilevered portion 117.

Additionally or alternatively, the angling of the cantilevered portion117 at an angle α of between 0 and 15° with respect to a planeperpendicular to the perimetral portion 116 may also aid easier and morereliable engagement of the substrate 110 with the headset 106 duringlifting of the substrate. Thus, some tolerance for lateral misalignmentof the substrate 110 with the headset 106 can be tolerated and adjustedfor by the angling of the cantilevered portion 117.

In FIG. 4 , a substrate 110 with a groove 114 is shown engaged in theheadset 106. The perimetral portion 116 may engage sealingly against theupper edge 107 of the substrate 110. This engagement may be with theinner edge 121 of the perimetral portion 116.

The cantilevered portion 117 may engage a region of the sidewall 108 ofthe substrate 110. As shown in FIG. 4 , preferably, the cantileveredportion 117 bridges over the gap 109 to hinder leakage of the washcoatout of the gap 109 and down the sidewall 108 of the substrate. Thecantilevered portion 117 may have a height of at least 5 mm greater thana depth of the gap 109 in the sidewall 108 of the substrate 110.

As noted above, the cantilevered portion 117 may have an arc length ofbetween 105 and 300% of an arc length of the gap 109 in the sidewall108, optionally between 105 and 200% of an arc length of the gap 109 inthe sidewall 108. In this way tolerance for some angular misalignment ofthe substrate 110 may be achieved, i.e. since the cantilevered portion117 will still be long enough to bridge over and fully seal the gap 109.

During operation of the substrate coating apparatus 101, a suction forceis applied to the lower surface of the substrate 110 using the vacuumcone. Advantageously, the flexibility and or relative thinness of thecantilevered portion 117 permits the cantilevered portion to be ‘sucked’into firmer engagement with the sidewall 108 by the suction force. Thisincrease the reliability of the seal between the cantilevered portion117 and the substrate 110.

During operation of the apparatus shown in FIG. 4 , as with thesubstrate coating apparatus 1, the washcoat passes through the dosingvalve 104 and inlet 122 into the showerhead cavity 124. The washcoatthen passes through the nozzle apertures 125 and drops down into contactwith the upper surface 112 of the substrate 110. The washcoat is thendrawn down through the passages of the substrate 110. Drawing of thewashcoat through the substrate 110 is driven, at least in part, by asuction force applied to the lower surface 113 of the substrate 110 bythe vacuum cone 7. During this process some washcoat may accumulate orpool in the groove 114. Washcoat may run along groove 114. However, theseal provided by the cantilevered portion 117 over the gap 109 preventsor substantially reduces any leakage of washcoat out of the gap 109 anddown the sidewall 108.

FIG. 10 illustrates certain aspects of the present disclosure wherein asubstrate coating apparatus is provided with a partition 200 interposedbetween the washcoat showerhead and an upper surface of the substrate.The partition 200 will be described in the following as part of thesubstrate coating apparatus 101 shown in FIGS. 4 to 9 by way of exampleonly. The partition 200 may be used in other substrate coatingapparatus. However, particularly beneficial effects may be achieved whenusing the partition 200 in combination with a headset seal 115 having acantilevered portion 117 as just described.

As shown most clearly in FIGS. 11 to 13 , the partition 200 comprises abody 205 comprising a plurality of holes 202. The body 205 may bedisc-shaped and may have an upper face 204 and a lower face 203. Thebody 205 of FIG. 12 is circular in shape. However, the partition 200 maybe other shapes and may be adapted to fit the size and shape of aparticular headset.

The partition 200 may have a thickness between the upper face 204 andthe lower face 203 of between 5 and 15 mm, optionally between 7.5 and12.5 mm, optionally 10 mm.

The partition 200 may comprise greater than 500 holes 202, optionallygreater than 1000 holes 202, optionally greater than 1500 holes 202,optionally greater than 2000 holes 202. The holes 202 may each bebetween 1 to 3 mm in diameter, optionally 2 mm in diameter. The holes202 may be arranged in a regular pattern or may be arrangedstochastically.

The percentage open area of the partition 200, defined as the percentageof the total area of the upper face 204 of the partition 200 that iscomprised by the holes 202, may be between 35 and 55%, optionallybetween 40 and 50%, optionally about 45%.

The partition 200 may be located in between the washcoat showerhead 105and the upper surface 112 of the substrate 110 when the substrate 110 isengaged in the headset 106 so as to maintain a first gap between thelower face 203 of the partition 200 and the upper surface 112 of thesubstrate 110. The first gap may be between 2 and 7 mm, optionally 5 mm.

Additionally or alternatively, the partition 200 may be located in theheadset 106 to maintain a second gap between a lower face of thewashcoat showerhead 105 and the upper face 204 of the partition. Thesecond gap may be between 80 and 130 mm.

Preferably, the partition 200 is fixedly located in the headset 106 soas to be held stationary relative to a housing of the headset 106.

The partition 200 may be formed from a metal, a plastic or other rigidmaterial. Non-limiting examples of suitable materials include polyvinylchloride (PVC), Acetal, Nylon 66 and Accura 25.

As shown in FIG. 10 , preferably the partition 200 is arranged in theheadset 106 above the headset seal 115.

In use, the substrate coating apparatus 101 incorporating the partition200 may be used in a method of coating a substrate 110 with a washcoat,wherein the method comprises the steps of:

-   -   engaging the substrate 110 with the headset 106 so as to locate        the upper surface 112 of the substrate 110 below the washcoat        showerhead 105 of the substrate coating apparatus 101;    -   arranging the partition 200 between the washcoat showerhead 105        and the upper surface 112 of the substrate 110, the partition        200 being located in the headset 106 to maintain the first gap        between the lower face 203 of the partition 200 and the upper        surface 112 of the substrate 110;    -   discharging a washcoat out of the washcoat showerhead 105 onto        the upper face 204 of the partition 200; and    -   passing the washcoat through the holes 202 in the partition 200,        onto the upper surface 112 of the substrate 110 and into the        substrate 110, at least in part by applying a suction force to        the lower surface 113 of the substrate 110.

EXAMPLES

FIG. 14 shows a side view of a substrate 110 that has had a washcoatapplied to it using a substrate coating apparatus 1 of the type shown inFIGS. 1 and 2 , i.e. without use of the headset seal 115 or thepartition 200 according to the present disclosure. As can be seen,during coating the washcoat 150 has leaked out of the gap 109 at the endof the groove 114 in the substrate and down the sidewall 108 of thesubstrate 110. Such leakage has resulted in this case in wastage ofwashcoat, soiling of the sidewall 108 of the substrate 110 and couldalso lead to obscuring of the visual identification markings 151 whichmay be provided on the sidewall 108 of the substrate.

FIG. 15 shows a top plan view of a substrate 110 that has had a washcoatapplied to it using a substrate coating apparatus 1 of the type shown inFIGS. 1 and 2 , i.e. without use of the headset seal 115 or thepartition 200 according to the present disclosure. As can be seen,during coating excess washcoat 150 has accumulated in portions of thegroove 114 which has not been adequately drawn into the passages by thevacuum. This can result in wastage of washcoat and blocking of some ofthe passages—resulting in an increased back pressure in use.

FIGS. 16 and 17 show, respectively, a side view of a sectioned substrate110 after coating with a washcoat and a bottom view of the substrate 110after coating but before sectioning. The washcoat was applied using asubstrate coating apparatus 1 of the type shown in FIGS. 1 and 2 , i.e.without use of the headset seal 115 or the partition 200 according tothe present disclosure. As can be seen in FIG. 16 , the washcoat profileproduced is very uneven, with a first portion 152 a of the profile whichis higher up the substrate 110 than a second portion 152 b. Indeed, inthis example the washcoat in the second portion 152 b of the profile hasreached all of the way to the lower surface 113 of the substrate 110resulting in ‘pull-through’ of the washcoat. This is also visible inFIG. 17 , where the region of ‘pull-through’ is shown by the darkerpatch. It will be noted that the second portion 152 b of the washcoatprofile is aligned with the groove 114, i.e. the washcoat has‘pulled-through’ the passages directly underneath the groove 114. Thiscan result in wastage of washcoat and also potential blocking of thepassage openings on the lower surface 113 of the substrate 110.

A comparative example to those of FIGS. 14 to 17 was carried out,wherein the washcoat was applied using a substrate coating apparatus 100of the present disclosure comprising the headset seal 115 and thepartition 200. The substrate was sectioned after coating with thewashcoat and a side view and an end view were analysed. It was foundthat using the substrate coating apparatus 100 of the present disclosurecomprising the headset seal 115 and the partition 200 produced awashcoat profile that was substantially more even than that shown inFIG. 16 and ‘pull-through’ of the washcoat, of the type shown in FIG. 17, was entirely prevented. In particular, use of the substrate coatingapparatus 100 of the present disclosure enabled an average coat depthacross the profile to be obtained that met a predetermined coat depthrequirement. There was also no hold up of washcoat in the groove of thesubstrate, of the type shown in FIG. 15 , and the channels of thesubstrate were not blocked with washcoat. There was also no or nosignificant amount of washcoat on the side of the substrate, unlike inthe example shown in FIG. 14 .

Further aspects and embodiments of the present disclosure are set out inthe following clauses:

Clause A1. A method of coating a substrate with a washcoat, wherein themethod comprises the steps of:

-   -   engaging the substrate with a headset of a substrate coating        apparatus so as to locate an upper surface of the substrate        below a washcoat showerhead of the substrate coating apparatus;    -   arranging a partition between the washcoat showerhead and the        upper surface of the substrate, the partition comprising a        plurality of holes and being located in the headset to maintain        a first gap between a lower face of the partition and the upper        surface of the substrate;    -   discharging a washcoat out of the washcoat showerhead onto an        upper face of the partition; and    -   passing the washcoat through the holes in the partition, onto        the upper surface of the substrate and into the substrate, at        least in part by applying a suction force to a lower surface of        the substrate.

Clause A2. The method of clause A1, wherein the partition is arranged ina fixed relationship in the headset.

Clause A3. The method of clause A1 or clause A2, wherein the first gapis between 2 and 7 mm, optionally 5 mm.

Clause A4. The method of any preceding clause, wherein the partition isdisc-shaped and has a thickness between its upper face and its lowerface of between 5 and 15 mm, optionally between 7.5 and 12.5 mm,optionally 10 mm.

Clause A5. The method of any preceding clause, wherein the partition islocated in the headset to maintain a second gap between a lower face ofthe washcoat showerhead and the upper face of the partition of between80 and 130 mm.

Clause A6. The method of any preceding clause, wherein the partitioncomprises greater than 500 holes, optionally greater than 1000 holes,optionally greater than 1500 holes, optionally greater than 2000 holes.

Clause A7. The method of any preceding clause, wherein the holes areeach between 1 to 3 mm in diameter, optionally 2 mm in diameter.

Clause A8. The method of any preceding clause, wherein the percentageopen area of the partition, defined as the percentage of the total areaof the upper face of the partition that is comprised by the holes, isbetween 35 and 55%, optionally between 40 and 50%, optionally about 45%.

Clause A9. The method of any preceding clause, wherein the headsetfurther comprises a headset seal and the partition is arranged in theheadset above the headset seal.

Clause A10. The method of any preceding clause, wherein the uppersurface of the substrate is non-planar.

Clause A11. The method of any preceding clause, wherein the uppersurface of the substrate comprises a shaping, for example a groove orcut-out, which extends to the sidewall of the substrate thereby defininga gap in the sidewall.

Clause A12. The method of any preceding clause, wherein the substrate isselected from a flow-through substrate (e.g. a monolithic flow-throughsubstrate) or a filter substrate (e.g. a wall-flow filter substrate).

Clause A13. The method of any preceding clause, wherein the washcoatcomprises a catalytic coating selected from a three way catalyst (TWC),a selective catalytic reduction (SCR) catalyst, a diesel oxidationcatalyst (DOC), a lean NOx trap catalyst (LNT), an ammonia slip catalyst(ASC), a combined selective catalytic reduction catalyst and ammoniaslip catalyst (SCR/ASC), and a passive NOx adsorber (PNA).

Clause A14. The method of any preceding clause, wherein the washcoat hasa viscosity of 3 to 9000 cP, optionally 3 to 54 cP, optionally 32 to 576cP, optionally 23 to 422 cP, optionally 250 to 4500 cP, optionally 500to 9000 cP.

Clause A15. The method of any preceding clause further comprising thesteps of any one of clauses B1 to B14.

Clause A16. A substrate coating apparatus comprising:

-   -   a source of a washcoat;    -   a washcoat showerhead for discharging the washcoat towards an        upper surface of a substrate;    -   a conduit fluidly connecting the source of the washcoat to the        washcoat showerhead for supplying washcoat to the washcoat        showerhead;    -   a headset for engaging the substrate to locate the upper surface        of the substrate below the washcoat showerhead; and    -   a vacuum generator for drawing the washcoat discharged from the        washcoat showerhead through the substrate;    -   wherein the headset comprises a partition comprising a plurality        of holes, the partition being located in between the washcoat        showerhead and the upper surface of the substrate when the        substrate is engaged in the headset so as to maintain a first        gap between a lower face of the partition and the upper surface        of the substrate.

Clause A17. A substrate coating apparatus according to clause A16,wherein the partition is fixedly located in the headset so as to be heldstationary relative to a housing of the headset.

Clause A18. A substrate coating apparatus according to clause A16 orclause A17, wherein the first gap is between 2 and 7 mm, optionally 5mm.

Clause A19. A substrate coating apparatus according to any one ofclauses A16 to A18, wherein the partition is disc-shaped and has athickness between its upper face and its lower face of between 5 and 15mm, optionally between 7.5 and 12.5 mm, optionally 10 mm.

Clause A20. A substrate coating apparatus according to any one ofclauses A16 to A19, wherein the partition is located in the headset tomaintain a second gap between a lower face of the washcoat showerheadand the upper face of the partition of between 80 and 130 mm.

Clause A21. A substrate coating apparatus according to any one ofclauses A16 to A20, wherein the partition comprises greater than 500holes, optionally greater than 1000 holes, optionally greater than 1500holes, optionally greater than 2000 holes.

Clause A22. A substrate coating apparatus according to any one ofclauses A16 to A21, wherein the holes are each between 1 to 3 mm indiameter, optionally 2 mm in diameter.

Clause A23. A substrate coating apparatus according to any one ofclauses A16 to A22, wherein the percentage open area of the partition,defined as the percentage of the total area of the upper face of thepartition that is comprised by the holes, is between 35 and 55%,optionally between 40 and 50%, optionally about 45%.

Clause A24. A substrate coating apparatus according to any one ofclauses A16 to A23, wherein the headset further comprises a headset sealand the partition is arranged in the headset above the headset seal.

Clause A25. A substrate coating apparatus according to any one ofclauses A16 to A24 further comprising the apparatus of any one ofclauses B16 to B29.

Clause A26. A substrate coating system comprising the substrate coatingapparatus of any one of clauses A16 to A25 and a substrate, wherein theupper surface of the substrate is non-planar; and optionally wherein theupper surface of the substrate comprises a shaping, for example a grooveor cut-out, which extends to the sidewall of the substrate therebydefining a gap in the sidewall.

Clause A27. A substrate coating system according to clause A26 furthercomprising the features of clause B31 or B32.

Clause A28. A partition configured for use in a substrate coatingapparatus, the partition comprising a disc-shaped body;

-   -   the disc-shaped body having a thickness between its upper face        and its lower face of between 5 and 15 mm, optionally between        7.5 and 12.5 mm, optionally 10 mm;    -   the partition comprising greater than 500 holes, optionally        greater than 1000 holes, optionally greater than 1500 holes,        optionally greater than 2000 holes;    -   the holes each being between 1 to 3 mm in diameter, optionally 2        mm in diameter;    -   wherein the percentage open area of the partition, defined as        the percentage of the total area of the upper face of the        partition that is comprised by the holes, is between 35 and 55%,        optionally between 40 and 50%, optionally about 45%.

Clause B1. A method of coating a substrate with a washcoat, wherein themethod comprises the steps of:

-   -   engaging the substrate with a headset of a substrate coating        apparatus so as to locate an upper surface of the substrate        below a washcoat showerhead of the substrate coating apparatus;    -   discharging a washcoat out of the washcoat showerhead towards        the upper surface of the substrate;    -   drawing the washcoat through the substrate by applying a suction        force to a lower surface of the substrate;        wherein the step of engaging the substrate with the headset        comprises engaging a headset seal of the headset with the        substrate, the headset seal comprising a perimetral portion        extending around the headset and a cantilevered portion        extending down from the perimetral portion which engages against        a sidewall of the substrate.

Clause B2. The method of clause B1, wherein the perimetral portioncomprises an annular portion, optionally a circular or oval portion,that extends fully around the headset.

Clause B3. The method of clause B1 or clause B2, wherein the uppersurface of the substrate is non-planar.

Clause B4. The method of any one of clauses B1 to B3, wherein thecantilevered portion is arc-shaped.

Clause B5. The method of any one of clauses B1 to B4, wherein the uppersurface of the substrate comprises a shaping, for example a groove orcut-out, which extends to the sidewall of the substrate thereby defininga gap in the sidewall, wherein the cantilevered portion bridges over thegap to hinder leakage of the washcoat out of the gap and down thesidewall of the substrate.

Clause B6. The method of clause B5, wherein the cantilevered portion hasan arc length of between 105 and 300% of an arc length of the gap in thesidewall, optionally between 105 and 200% of an arc length of the gap inthe sidewall.

Clause B7. The method of any one of clauses B1 to B6, wherein thecantilevered portion subtends a central angle of between 45 and 120°,optionally between 45 and 90°, optionally between 65 and 75°.

Clause B8. The method of any one of clauses B1 to B7, wherein thecantilevered portion extends at an angle of between 0 and 15° withrespect to a plane perpendicular to the perimetral portion; optionallyat an angle of between 0 and 10° with respect to a plane perpendicularto the perimetral portion; optionally at an angle of about 3° withrespect to a plane perpendicular to the perimetral portion.

Clause B9. The method of any one of clauses B1 to B8, wherein onengaging the substrate with the headset, the cantilevered portion of theheadset seal flexes in a substantially radial direction.

Clause B10. The method of any one of clauses B1 to B9, wherein a loweredge of the cantilevered portion freely projects and is thus enabled toflex in a substantially radial direction.

Clause B11. The method of any one of clauses B1 to B10, wherein thecantilevered portion engages a region of the sidewall of the substratehaving a height of at least 5 mm greater than a depth of a gap in thesidewall of the substrate.

Clause B12. The method of any one of clauses B1 to B11, wherein thecantilevered portion extends down at least 20 mm below a lower face ofthe perimetral portion, optionally at least 30 mm below a lower face ofthe perimetral portion, optionally at least 40 mm below a face rim ofthe perimetral portion.

Clause B13. The method of any one of clauses B1 to B12, wherein thesubstrate is selected from a flow-through substrate (e.g. a monolithicflow-through substrate) or a filter substrate (e.g. a wall-flow filtersubstrate).

Clause B14. The method of any one of clauses B1 to B13, wherein thewashcoat comprises a catalytic coating selected from a three waycatalyst (TWC), a selective catalytic reduction (SCR) catalyst, a dieseloxidation catalyst (DOC), a lean NOx trap catalyst (LNT), an ammoniaslip catalyst (ASC), a combined selective catalytic reduction catalystand ammonia slip catalyst (SCR/ASC), and a passive NOx adsorber (PNA).

Clause B15. The method of any one of clauses B1 to B14, furthercomprising the steps of any one of clauses A1 to A14.

Clause B16. A substrate coating apparatus comprising:

-   -   a source of a washcoat;    -   a washcoat showerhead for discharging the washcoat towards an        upper surface of a substrate;    -   a conduit fluidly connecting the source of the washcoat to the        washcoat showerhead for supplying washcoat to the washcoat        showerhead;    -   a headset for engaging the substrate to locate the upper surface        of the substrate below the washcoat showerhead; and    -   a vacuum generator for drawing the washcoat discharged from the        washcoat showerhead through the substrate;    -   wherein the headset comprises a headset seal for engaging        against the substrate, the headset seal comprising a perimetral        portion that extends around the headset and a cantilevered        portion that extends down from the perimetral portion and which        is configured to engage against a sidewall of the substrate.

Clause B17. A substrate coating apparatus according to clause B16,wherein the perimetral portion comprises an annular portion, optionallya circular or oval portion, that extends fully around the headset.

Clause B18. A substrate coating apparatus according to clause B16 orclause B17, wherein the cantilevered portion engages a region of thesidewall of the substrate having a height of at least 5 mm greater thana depth of a gap in the sidewall of the substrate.

Clause B19. A substrate coating apparatus according to any one ofclauses B16 to B18, wherein the cantilevered portion extends down atleast 20 mm below a lower face of the perimetral portion, optionally atleast 30 mm below a lower face of the perimetral portion, optionally atleast 40 mm below a face rim of the perimetral portion.

Clause B20. A substrate coating apparatus according to any one ofclauses B16 to B19, wherein the cantilevered portion extends at an angleof between 0 and 15° with respect to a plane perpendicular to theperimetral portion; optionally at an angle of between 0 and 10° withrespect to a plane perpendicular to the perimetral portion; optionallyat an angle of about 3° with respect to a plane perpendicular to theperimetral portion.

Clause B21. A substrate coating apparatus according to any one ofclauses B16 to B20, wherein the headset comprises a rigid headset framesupporting the perimetral portion of the headset seal and thecantilevered portion of the headset seal extends below a lower face ofthe rigid headset frame.

Clause B22. A substrate coating apparatus according to any one ofclauses B16 to B21, wherein a lower edge of the cantilevered portionfreely projects from the rigid headset frame.

Clause B23. A substrate coating apparatus according to any one ofclauses B16 to B22, wherein the cantilevered portion is arc-shaped.

Clause B24. A substrate coating apparatus according to any one ofclauses B16 to B23, wherein the cantilevered portion subtends a centralangle of between 45 and 120°, optionally between 45 and 90°, optionallybetween 65 and 75°.

Clause B25. A substrate coating apparatus according to any one ofclauses B16 to B24, wherein the cantilevered portion has a depth, in aradial direction, of between 2.5 to 5.0 mm.

Clause B26. A substrate coating apparatus according to any one ofclauses B16 to B25, wherein the perimetral portion and the cantileveredportion are formed unitarily.

Clause B27. A substrate coating apparatus according to any one ofclauses B15 to B24, wherein the perimetral portion and the cantileveredportion are separate.

Clause B28. A substrate coating apparatus according to any one ofclauses B16 to B27, wherein the perimetral portion and the cantileveredportion are formed of different materials.

Clause B29. A substrate coating apparatus according to any one ofclauses B16 to B28, wherein the cantilevered portion has a shorehardness of between 35 A and 45 A, optionally of 40 A.

Clause B30. A substrate coating apparatus according to any one ofclauses B16 to B29 further comprising the apparatus of any one ofclauses A16 to A24.

Clause B31. A substrate coating system comprising the substrate coatingapparatus of any one of clauses B16 to B30 and a substrate, wherein theupper surface of the substrate is non-planar.

Clause B32. A substrate coating system according to clause B31, whereinthe upper surface of the substrate comprises a shaping, for example agroove or cut-out, which extends to the sidewall of the substratethereby defining a gap in the sidewall.

Clause B33. A substrate coating system according to clause B31 or B32further comprising the features of clause A26 or A27.

Clause B34. A headset seal for engaging against a substrate, the headsetseal comprising a perimetral portion for extending around a headset anda cantilevered portion that extends from the perimetral portion andwhich is configured for engaging against a sidewall of a substrate.

Clause B35. A headset seal according to clause B34, wherein thecantilevered portion is arc-shaped.

Clause B36. A headset seal according to clause B34 or clause B35,wherein the cantilevered portion subtends a central angle of between 45and 120°, optionally between 45 and 90°, optionally between 65 and 75°.

Clause B37. A headset seal according to any one of clauses B34 to B36,wherein the cantilevered portion has a depth, in a radial direction, ofbetween 2.5 to 5.0 mm.

Clause B38. A headset seal according to any one of clauses B34 to B37,wherein the perimetral portion and the cantilevered portion are formedunitarily.

Clause B39. A headset seal according to any one of clauses B34 to B37,wherein the perimetral portion and the cantilevered portion areseparate.

Clause B40. A headset seal according to any one of clauses B34 to B39,wherein the perimetral portion and the cantilevered portion are formedof different materials.

Clause B41. A headset seal according to any one of clauses B34 to B40,wherein the cantilevered portion has a shore hardness of between 35 Aand 45 A, optionally of 40 A.

The invention claimed is:
 1. A substrate coating apparatus comprising: asource of a washcoat; a washcoat showerhead for discharging the washcoattowards an upper surface of a substrate; a conduit fluidly connectingthe source of the washcoat to the washcoat showerhead for supplyingwashcoat to the washcoat showerhead; a headset for engaging thesubstrate to locate the upper surface of the substrate below thewashcoat showerhead; and a vacuum generator for drawing the washcoatdischarged from the washcoat showerhead through the substrate; whereinthe headset comprises a partition comprising a plurality of holes, thepartition being located in between the washcoat showerhead and the uppersurface of the substrate when the substrate is engaged in the headset soas to maintain a first gap between a lower face of the partition and theupper surface of the substrate.
 2. The substrate coating apparatusaccording to claim 1, wherein the partition is fixedly located in theheadset so as to be held stationary relative to a housing of theheadset.
 3. The substrate coating apparatus according to claim 1,wherein the first gap is between 2 and 7 mm.
 4. The substrate coatingapparatus according to claim 1, wherein the percentage open area of thepartition, defined as the percentage of the total area of the upper faceof the partition that is comprised by the holes, is between 35 and 55%.5. The substrate coating apparatus according to claim 1, wherein thepercentage open area of the partition, defined as the percentage of thetotal area of the upper face of the partition that is comprised by theholes, is between 40 and 50%.
 6. The substrate coating apparatusaccording to claim 1, wherein the headset further comprises a headsetseal and the partition is arranged in the headset above the headsetseal.
 7. A substrate coating system comprising the substrate coatingapparatus of claim 1 and a substrate, wherein the upper surface of thesubstrate is non-planar; and wherein the upper surface of the substratecomprises a groove or cut-out, which extends to the sidewall of thesubstrate thereby defining a gap in the sidewall.